This invention relates to actinide recovery. More particularly, it relates to the removal of americium and all forms of plutonium from solutions such as plutonium scrap recovery nitric acid waste streams.
The separation of actinides from acid aqueous solutions, using a solvent sorbed onto a solid, is well known. Thus, Fuller discloses the extraction of uranium values from solution, using agglomerates of e.g., trioctylphosphine oxide (TOPO) and solid particles such as polystyrene, p-terphenyl, polyethylene, and the like (U.S. Pat. No. 4,406,865). Delvalle, also, has disclosed differential complex formation of uranium isotopes by phosphine oxides, etc., including TOPO (U.S. Pat. Nos. 4,012,480 and 4,237,100). Pyrih et al, in uranium recovery from phosphoric acid solutions, separate alkylphenylphosphate esters by adsorption on particles of polystyrene, followed by elution of said esters with methanol (U.S. Pat. No. 4,305,912). It is also known that plutonium polymers can be extracted by liquid bifunctional organophosphorus compounds such as dibutylphosphate (DBP) and dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP), as disclosed and reviewed by Muscatello et al in Separation Science and Technology, 18 (14 & 15), pp. 1731-6 (1983), incorporated herein by reference. These are the only successful liquid-liquid plutonium polymer extractions known to applicants, through their own experience (with DHDECMP) or from the literature (DBP, published between 1956 and 1963. See reference 4 to 6 of the Muscatello et al paper, supra).
Yet, in the conventional handling of actinide solutions for recovery of their metal values, the formation of plutonium polymers is carefully avoided because of the difficulties involved in their separation from solution and their resistance, once formed, to conversion to more easily removable non-polymeric species. In practice, uranium polymer formation is prevented by working in acid medium. As a result of these circumstances, the problem of removing plutonium polymers from aqueous solution has not yet been specifically addressed.
It is therefore an object of this invention to provide a process for removal of actinides including all forms of plutonium from aqueous solutions.
Additional objects, advantages, and novel features of the invention will be set forth in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following disclosure, or still may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.